Protection technologies, which are mainly used for realizing a redundancy backup between a main path and a backup path, have been extensively employed in the practical application of an Ethernet. When the main path and the backup path are both in good condition, the protected data forwarding function of the backup path is disabled, and the protected data between networks are transmitted on the main path. When the main path is failed, the protected data forwarding function of the backup path is enabled, and the transmission of the protected data between networks is switched to be completed by the backup path. the above protection processing is capable of preventing the protected data from being received repeatedly or generating a broadcast storm when the network is in a normal state, and capable of activating the backup path to transmit the protected data when the main path of the network is failed, then the failure resistance of the Ethernet is improved, and the high real-time requirement on a convergence time of shorter than 50 ms during a switching is met.
An example is given below for illustrating the implementation process of the protection technologies for a multi-ring Ethernet. FIG. 1 is a schematic diagram illustrating the topology of a multi-ring Ethernet according to related technologies. As shown in FIG. 1, nodes S1-S6 are all Ethernet switches. Node S1 is correspondingly provided with ports 11 and 12; node S2 is correspondingly provided with ports 21, 22 and 23; node S3 is correspondingly provided with ports 31, 32 and 33; node S4 is correspondingly provided with ports 41, 42 and 43; node S5 is correspondingly provided with ports 51, 52 and 53; node S6 is correspondingly provided with ports 61 and 62; network B is connected with node S2; and network A is connected with node S5. Four physical communication paths are provided between network A and network B, i.e. path 1: network A<->node S5<->node S3<->node S2<->network B; path 2: network A<->node S5<->node S3<->node S4<->node S1<->node S2<->network B; path 3: network A<->node S5<->node S6<->node S4<->node S3<->node S2<->network B; and path 4: network A<->node S5<->node S6<->node S4<->node S1<->node S2<->network B.
In the application of the protection technologies for a multi-ring Ethernet, a ring network domain is defined firstly. FIG. 2 is a schematic diagram illustrating the topology of a communication path when links in a multi-ring Ethernet are in good condition according to related technologies. As shown in FIG. 2, a main ring and a sub-ring are included in a ring network domain. The main ring includes nodes S1-S4 and includes links between nodes S1 and S2, between nodes S2 and S3, between nodes S3 and S4, and between nodes S4 and S1. The sub-ring includes nodes S3, S5, S6 and S4 and includes links between nodes S3 and S5, between nodes S5 and S6, and between nodes S6 and S4. Moreover, a ring protection link, main nodes (or known as control nodes) the ring protection link belongs to, and main ports and slave ports of the main nodes are also defined, wherein a link directly connected with the slave ports of a main node is a ring protection link. The main node of the main ring is S1, which correspondingly has a main port 12 and a slave port 11; and the main node of the sub-ring is S6, which correspondingly has a main port 61 and a slave port 62. When links in the ring network domain of the multi-ring Ethernet are in good condition, the main nodes of the main ring and the sub-ring disable the protected data forwarding function of the slave ports, node S1 disables the protected data forwarding function of slave port 11, and node S6 disables the protected data forwarding function of slave port 62, then the communication path between networks B and A is as follows: network B<->node S2<->node S3<->node S5<->network A.
FIG. 3 is a schematic diagram illustrating the topology of a communication path when a link failure occurs in a multi-ring Ethernet according to related technologies. As shown in FIG. 3, node S1 in a main ring is a main node, port 12 of node S1 is a main port, port 11 of node S1 is a slave port, and a link directly connected with port 11 is a ring protection link of the main ring; and node S6 in a sub-ring is a main node, port 61 of node S6 is a main port, port 62 of node S6 is a slave port, and a link directly connected with port 62 is a ring protection link of the sub-ring. Under normal condition, the main nodes of the main ring and the sub-ring disable the protected data forwarding function of their slave ports to avoid the transmission of the protected data on a protection link so as to prevent the repeated forwarding of the protected data and the occurrence of a broadcast storm. If a link failure occurs in the ring network domain of the multi-ring Ethernet and the failed link is not a protection link, then the main nodes enable the protected data forwarding function of the slave ports, each node is required to refresh an address forwarding table, and the communication between networks is carried out on a new path. As shown in FIG. 3, in the event that the link between nodes S2 and S3 on the main ring is failed, after detecting the link failure, node S2 disables the data forwarding function of port 22 and notifies other nodes of the link failure, then node S1 enables the protected data forwarding function of port 11 after receiving the failure notice; is in addition, each node in the ring network domain is required to refresh an address forwarding table, and the new communication path between networks B and A is as follows: network B<->node S2<->node S1<->node S4<->node S3<->node S5<->network A.
A recovery switching is needed when the failed link in the ring network domain of the multi-ring Ethernet is recovered so that the network transmission is recovered to be performed on the transmission path used under normal condition, and as the path is changed, the nodes are required to refresh the address forwarding table.
A large number of control messages are transmitted in a control virtual local area network (VLAN for short) in the ring network domain when the multi-ring Ethernet is in maintenance or protection switching. There are two kinds of control VLANs: a main control VLAN corresponding to a main ring, and a sub-control VLAN corresponding to a sub-ring. Control messages of the main ring are transmitted in the main control VLAN, while control messages of the sub-ring are transmitted in the sub-control VLAN. FIG. 4 is a schematic diagram illustrating the control VLANs of the main ring and the sub-ring of the multi-ring Ethernet according to related technologies. As shown in FIG. 4, the main control VLAN is VLAN 3, the sub-control VLAN is VLAN 4, the ring network port of the main ring belongs to both VLAN 3 and VLAN 4, and the ring network port of the sub-ring only belongs to VLAN 4. Under this mechanism, control messages of the main ring are forwarded only inside the main ring, while control messages of the sub-ring can be transmitted through the main ring. Although the system operation is simplified based on the transmission mode in which control messages of the sub-ring can be transmitted through the main ring, this mechanism has the following two problems.
Problem 1: the processing of a main ring node on a protocol message (i.e., a control message) of the sub-ring needs extra time, which clashes with the high real-time requirement of the multi-ring Ethernet on a convergence time of shorter than 50 ms during a networking switching. This problem is described below in combination with FIG. 5 and FIG. 6. In FIG. 5 and FIG. 6, a main ring is a ring including nodes S1-Sn, wherein node S1 is a main node, port 12 of node S1 is a slave port, and a link directly connected with slave port 12 is a ring protection link of the main ring; and a sub-ring is a ring including nodes M1, M2, S2 and S3, wherein nodes M1 is a main node of the sub-ring, port 12 of node M1 is a slave port, and a link directly connected with slave port 12 is a ring protection link of the sub-ring.
FIG. 5 is a first schematic diagram illustrating a control message forwarding analysis carried out when a link of a sub-ring is in a protection switching according to related technologies. As shown in FIG. 5, a link between nodes M2 and S2 is failed if a loop of a sub-ring is failed, after detecting the failure, the adjacent nodes M2 and S2 disable the data forwarding function of the protected VLANs of port 21 of node M2 and port 23 of node S2, and nodes M2 and S2 send a control message LINK-DOWN to main node M1 of the sub-ring. During this phase, the control message LINK-DOWN is processed on the main ring node for 2δ (δ is the control message processing time of a single node).
FIG. 6 is a second schematic diagram illustrating a control message forwarding analysis carried out when a link of a sub-ring is in a protection switching according to related technologies. As shown in FIG. 6, after receiving the control message LINK-DOWN, main node M1 enables the VLAN-protecting data forwarding function of a slave port and sends a control message FLUSH-DOWN to notify each node to update an MAC (media access control) address, and each node updates the MAC address, then a failure switching is completed. In this phase, the control message FLUSH-DOWN of the sub-ring is processed on the main ring node for nδ (n is the number of the nodes on the main ring, and δ is the control message processing time of a single node). Therefore, when the multi-ring Ethernet is in a protection switching, the control message of the sub-ring is processed by a node for (n+2)δ in the main ring.
FIG. 7 is a first schematic diagram illustrating a control message forwarding analysis carried out when a failed link of a sub-ring is in a recovery switching according to related technologies. As shown in FIG. 7, when a failed link is recovered, the link failure between nodes S2 and M2 is removed, the adjacent nodes S2 and M2 detect the failure removal, a control message HELLO sent by main node M1 of the sub-ring passes through the failure-removed link, and slave port 12 of main node M1 detects the message HELLO sent by itself. And a protected VLAN-protecting data message can still pass through the slave port of main node M1, the protection protocol of the multi-ring Ethernet is not switched, and no frame is lost. In this phase, the control message HELLO of the sub-ring is processed on a main ring node for 2δ (δ is the control message processing time of a single node), and a switching is started after the message HELLO is received by main node M1.
FIG. 8 is a second schematic diagram illustrating a control message forwarding analysis carried out when a failed link of a sub-ring is in a recovery switching according to related technologies. As shown in FIG. 8, main node M1 disables the VLAN-protecting data forwarding function of a slave port and sends a message FLUSH-UP to notify each node to carry out a recovery switching, the failure-removed link enables the VLAN-protecting data forwarding function of a corresponding port, and each node updates its MAC address, then the recovery switching is completed. In this phase, a control message FLUSH-UP of the sub-ring is processed on a main ring node for nδ (n is the number of the nodes on the main ring, and δ is the control message processing time of a single node). Therefore, it can be seen that a control message of the sub-ring is processed by a node for (n+2)δ in a main ring when a multi-ring Ethernet is in a recovery switching.
It can be seen from the above example that the sub-ring control message processing time δ of a main ring node has a significant influence on the switching time of a multi-ring Ethernet, so the proposal of a new processing mode for the main ring node to process a sub-ring control message has extraordinary meaning in improving the performance of a multi-ring Ethernet.
Problem 2: a data loop is easily caused by control messages of the sub-ring. FIG. 9 is a schematic diagram illustrating the generation of a loop by control messages of a sub-ring in a main ring according to related technologies. As shown in FIG. 9, a main ring consists of nodes S1-S6, and a sub-ring consists of nodes S2, S3, S7 and S8. Under normal condition, slave port 12 of main node S1 on the main ring is blocked for data VLAN (but not for a control message) to prevent the protected data generating a broadcast storm; and for the same sake, slave port 72 of main node S7 on the sub-ring is also blocked for data VLAN (but not for a control message). After the sub-ring is failed, main node S7 of the sub-ring sends a message HELLO from its main port 71 to detect whether the loop is recovered, and the loop is considered recovered if node S7 can receive the message HELLO from its slave port within a given period of time. After sent from the main node of the sub-ring, the control message HELLO of the sub-ring is transmitted on the following paths: path 1: the main port of node S7<->node S8<-> node S2<->node S3<->the slave port of node S7; and path 2: the main port of node S7<->node S8<->node S2<->node S1<->node S6<->node S5<->node S4<->node S3<->node S2. In path 2, the control message HELLO of the sub-ring forms a data loop in the main ring because slave port 12 of main node S1 on the main ring is blocked for a data message but not for a control message under normal condition; after receiving the message HELLO of the sub-ring, slave port 12 of main node S1 determines whether the message HELLO is a control message of the main ring; if not, the message HELLO is immediately forwarded from the main port, then it leads to a repeated forwarding of the message HELLO in the main ring, a bandwidth waste of the main ring, and even the generation of a broadcast storm by the control message of the sub-ring on the main ring if the situation gets worse.
It can be seen from above description that a main ring node needs extra time to process a control message of a sub-ring in existing control message transmission process, and transmitting the control message of the sub-ring on a main ring will cause a loop problem. However, no effective solution has been provided yet to solve the problems